External walls of large structures such as buildings have been finished by directly applying a coating or tiling to a surface of a concrete body at a construction site or, as in a curtain wall, by precast-molding or connecting a concrete body and a finishing material at a factory and fabricating at the construction site.
On the other hand, for an external wall of a structure such as a house, large panels, such as siding boards subjected to premolding and precoating to form an irregular external surface, fixed on a stud or a base panel made of wood or steel, has been generally widespread.
For example, in case of ceramic siding boards which are most frequently used as external wall materials of houses, the boards are generally installed by adhering or connecting through post treatment engagement fittings on a wall of the house through a stud or a base panel made of wood or steel.
Although use of such siding boards improves a design of external walls and allows a variety in terms of selection of design, adhesion or connection of the engagement fittings through post treatment and installation of the boards onto a surface of an external wall were laborious and costly, and were great restriction factors in terms of construction and cost.
Thus, mold-integrating of the engagement fittings during molding of the siding boards has been studied. However, ordinary cement or ceramic sidings have been problematic in that, in such mold-integrating, warpage and cracks could not be avoided during cure shrinkage of these products.
Meanwhile, in some ALC panels and precast concrete panels having a thickness of more than 50 mm, an example of mold-integrating and embedding by first welding and fixing an engagement fitting to reinforcement steel and then pouring ready-mixed concrete, is known. Here, the reinforcement steel and fittings to be embedded are located on a surface and a back at a nearly central position, or a nearly symmetrical position from a center of a cured product, to prevent warpage and cracks by cure shrinkage. However, such ALC panels and pre-cast concrete panels have an artificial appearance with little natural texture, and are also heavy in terms of weight. Also, a shape and position of the fittings were characteristically restricted.
Under these circumstances, as a product that can realize designs with a more natural texture, an artificial stone, which is a molded product of a mixture of resin, natural stone and mineral, has attracted much attention, and attempts have been made to mold-integrate engagement fittings on such an artificial stone. For example, JP-A-6-106549 proposes a method in which a fitting for engagement is held from both a surface and back by mold-laminating with a molten material obtained by kneading a thermosetting resin and a stone powder. Balance of cure shrinkage of the surface and the back is attempted to suppress warpage. Nevertheless, in this case, only a simple mold-lamination process is attempted, and this molding method is limited. Further, because a relationship between composition of a molded product and integration with a fitting has not been taken into consideration, occurrence of warpage and cracks following integration is not satisfactorily suppressed. Moreover, design properties and physical properties such as strength for using this artificial stone as an external wall material is not actually taken into consideration.
Consequently, an object of the invention of this application is to provide, upon solving the foregoing problems associated with the prior art, a novel artificial stone wall panel as an external wall material with excellent design, while also simplifying installation to an external wall, thereby being advantageous in view of productivity, workability and cost, by mold-integrating an artificial stone and structure for installing such artificial stone to an external wall surface. An object of the invention of this application is also to provide a process for producing the artificial stone wall panel.